Functionalized thermoplastic elastomer

ABSTRACT

A thermoplastic elastomer produced without a hydrogenation step is functionalized utilizing a free radical initiator and a functionalizing monomer having at least one point of unsaturation. The base polymers can be produced by copolymerizing an α-olefin capable of producing an amorphous backbone with a comonomer which provides a “hook” for grafting to with a living polystyrene chain. Another method is to copolymerize an α-olefin monomer system capable of producing an amorphous backbone with a comonomer containing a functional group from which an anionically polymerizable monomer is grown from the backbone. A third method involves copolymerizing an α-olefin monomer system capable of giving an amorphous backbone with an olefin-terminated polystyrene comonomer. In a less preferred embodiment, a conventional EPDM polymer can be metallated and a monoalkenyl aromatic compound anionically polymerizable monomer grown from the backbone.

This is a continuation division continuation-in-part of application Ser.No. 09/872,625 filed Jun. 1, 2001, now U.S. Pat. No. 6,552,125 which isa division of Ser. No. 09/502,646 filed Feb. 11, 2000, now U.S. Pat. No.6,319,990, which is a division of Ser. No. 09/080,822 filed May 18,1998, now U.S. Pat. No. 6,100,337, the entire disclosure of which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

This invention relates to functionalized polymers.

Synthetic polymers are generally characterized as either resinous orelastomeric. Historically, elastomeric polymers required chemicalvulcanization before they possessed sufficient strength for utilitiessuch as tire treads, shoe soles, rubber bands, and other elasticutilities requiring some level of strength. However, these compositionsafter vulcanization were no longer thermoplastic.

In the 1960s a major advance in the art occurred with the discovery andcommercialization of thermoplastic elastomers. These materials possessan internal elastomeric block and a plurality of terminal aromaticblocks. On cooling from a melt, such compositions exhibit high tensilestrength, high elongation, and rapid and almost complete recovery afterelongation. This is attributed to the fact that in the bulk state, thearomatic end segments of these block copolymers agglomerate. Attemperatures significantly below the glass transition temperature(T_(g)) of the aromatic end blocks, these agglomerations (domains) actas strong, multifunctional junction points and so the copolymers behaveas though they are joined in a cross-linked network.

Such polymers are non-polar and hence are sometimes not ideally suitedfor applications that require adhesion to polar substrates or thatrequire compatibility with polar polymeric materials. This can beovercome by incorporating a functional group on the polymer. However,these polymers contain a large amount of aliphatic unsaturation in thediene blocks which can result in cross-linking and gellation of polymerchains during the free-radical grafting reactions used to incorporatepolar functional groups. Hence, it is necessary to utilize ahydrogenation step prior to incorporating a functional group.Hydrogenation can be accomplished using any of several hydrogenationprocesses known in the art. For instance, the commonly used method is toemploy a Group VIII metal catalyst, particularly nickel or cobalt, witha suitable reducing agent such as an aluminum alkyl to catalyze thehydrogenation. The disadvantage in this is the necessity for theadditional hydrogenation and catalyst removal steps. These steps areequipment and time intensive and thereby increase the complexity andcost of producing functionalized thermoplastic-plastic elastomers. Inaddition, the hydrogenation catalysts are sensitive to certain poisons,making hydrogenation of polymers containing particular functional groupsor coupling agent residues difficult or impossible.

Thus, it would be highly desirable to have a process by whichfunctionalized thermoplastic elastomers could be directly producedwithout the necessity of a hydrogenation step.

SUMMARY OF THE INVENTION

It is an object of this invention to provide functionalizedthermo-plastic elastomers without the utilization of a hydrogenationstep.

In accordance with this invention a thermoplastic elastomer is preparedwith an amorphous olefin or EPDM backbone and a plurality of pendantaromatic side chains and thereafter contacted with a reactive functionalmonomer in the presence of a free radical initiator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Surprisingly, it has been found that even though α-olefin amorphousbackbones inherently contain a regular pattern of alkyl side chainswhich are a potential source of Beta-scission, thermoplastic elastomershaving such backbones can be functionalized and still retain asignificant amount of strength.

Amorphous Backbone

There are two embodiments to this invention. In the first and preferredembodiment there is an all α-olefin amorphous backbone. In thisembodiment the backbone is made of an olefin monomer or a mixture ofolefin monomers and a comonomer. The monomer is either a C₄ to C₃₀α-olefin (or mixtures thereof) or ethylene and a higher α-olefin secondmonomer (higher than ethylene, i.e. C₃ and higher). As a practicalmatter, the second monomer will almost always be a C₃ to C₅ α-olefinsince there would be little point in utilizing a C₆ or higher secondmonomer since an amorphous backbone can be made directly from a C₆α-olefin, if desired. Broadly, however, the second monomer can be any C₃to C₃₀ α-olefin. The preferred monomers are hexene, octene,ethylene/propylene and ethylene/butene. When the backbone is made from acombination of ethylene and a C₃ or higher α-olefin, the C₃ or higherα-olefin is used in a mole ratio of 20 to 40, preferably 30 to 40, morepreferably 30 to 35 percent.

There are three aspects to this first embodiment of the invention. Inthe first aspect, the comonomer is a 1-alkenyl compound containing afunctional group to which an anionic polymer can be grafted “to” toproduce a pendant graft block side chain.

Suitable comonomers are those having the formula

CH₂═CH—(CH₂)_(n)—Y

where n≧0 and Y is selected from the group including halosilane groups,hydridosilane groups, ester groups, aldehyde groups, ketones, halogens,epoxides, and phosphorous groups of the formula P-Z₂ where Z is Cl, Br,I, F, hydrogen, ester groups, or combinations of these.

The preferred 1-alkenylhalosilane compounds which can be used in thepresent invention include H₂C═CH—(CH₂)_(n)—SiX₃ where n≧0; X=halogen, Ror H or combinations thereof, R is alkyl, or aryl; and at least one Xmust be halogen. This definition of R is in the context of a1-alkenylhalosilane, R being used in other contexts hereinafter.Similarly X is used in another context later. H₂C═CH—(CH₂)_(n)—SiMe₂Clis preferred because when the presence of ungrafted anionic polymer inthe final product is undesirable, this halosilane may easily be removedfrom the backbone copolymer due to its high volatility.

Also preferred for the same reason are hydrosilane compounds of theformula

CH₂═CH—(CH₂)_(n)SiH_(x)R_(y)

where n≧0, x+y=3, x≧1, and y≦2. Most preferred compounds have thesestructures: CH₂═CH—CH₂—SiH₃, CH₂═CH—SiH₃, CH₂═CH—SiH₂CH₃, andCH₂═CH—CH₂—SiH₂CH₃. In the last two structures halogen may take theplace of H, in which case the silanes would be halosilanes.

In the second aspect of this first embodiment, the comonomer is a vinylaromatic compound represented by the general formula

wherein n is an integer of 0 to 20, or an alkenyl alkyl or aryl silanerepresented by the formula:

CH₂═CH—(CH₂)_(n)—SiR_(m)H_(x)  (2)

where n is 0 or an integer of from 1 to 12; R is alkyl or aryl,preferably methyl, phenyl, or ethyl; x is 0 or 1; m is 2 or 3; and x+m3. The most preferred alkenyl silanes for use herein areallyltrimethylsilane and allyl dimethylsilane because they are mostreactive to copolymerization with α-olefins. This forms a copolymerwhich becomes the backbone of the graft block copolymer of the presentinvention.

In this aspect of the first embodiment, the comonomer contains afunctional group. In the case of the first formula, the benzylic carbonatom imparted by the comonomer can be deprotonated by a metallatingagent such as RLi and the resulting structure behaves in a mannersimilar to styrene anions. Thus, while the vinyl aromatic comonomermight not normally be thought of as imparting a functional group onincorporation into the polymer chain, the benzylic hydrogen isfunctional to the metallating agent. In the case of the second formula,the R group can be deprotonated by the metallating agent. From thismetallated functional group a monovinyl arene anionically polymerizablemonomer is grown “from” the backbone to form pendant aromatic sidechains.

In the third aspect of this first embodiment of the invention, thecomonomer is an olefin capped aromatic polymer chain utilized to givearomatic side chains of sufficient length and number to form resinous orglassy domains. The comonomer is produced by anionic polymerization of amonoalkenyl aromatic compound having 8 to 20 carbon atoms with alkenylgroups of up to 3 carbon atoms attached to a benzene ring as exemplifiedby styrene and styrene homologs such as ethylvinylbenzene,α-methylstyrene and paramethylstyrene. Styrene and α-methylstyrene areparticularly preferred monoalkenyl aromatic compounds, especiallystyrene.

The initiator systems used in the first step of producing thesemacromonomers are those conventionally used in the art. They generallyare those of the general formula RLi where R is a hydrocarbyl radical of1 to about 20 carbon atoms. This is the definition of R in the contextof RLi, R being used later in a different context. Examples of suchlithium initiators are methyllithium, isopropyllithium, n-butyllithium,sec-butyllithium, t-butyllithium, n-dodecyllithium, cyclohexyllithium,and 4-cyclohexyllithium. Preferred are n-butyllithium andsec-butyllithium. The amount of the lithium metal initiator employeddepends upon the desired molecular weight of the macromonomer. Normally,the organomonollithium initiator is employed in the range of about 0.1to 200, preferably 2 to 30 millimoles per 100 grams of total monoalkenylaromatic monomer.

The polymerization reaction to produce the comonomer (macromer)precursor can be carried out in the presence of a hydrocarbon diluent.Preferably the hydrocarbon diluent is a paraffinic, cyclo-paraffinic oraromatic hydrocarbon having 4-10 carbon atoms or a mixture of suchdiluents. Examples for the diluent are n-hexane, n-heptane,2,2,4-trimethylpentane, cyclohexane, benzene and toluene. Cyclohexane isgenerally the preferred paraffinic solvent.

It is preferred, however, to carry out the initiation of the aromaticmacromonomer precursor in the presence of an α-olefin diluent andthereafter to end cap the resulting alkali metal terminated livingpolymer chain in the presence of the same diluent.

The reaction is generally carried out with a weight ratio of diluent tomonomers exceeding 1. Preferably the diluent is employed in a quantitybetween about 2 to about 20 parts by weight, most perfably 3 to 10 partsby weight, per 1 part by weight of total anionically polymerizablemonomers. The term “anionically polymerizable monomer” refers to themonomer utilized to prepare the comonomer precursor.

The polymerization to produce the macromer precursor usually occurswithin a period of time ranging from 1 minute up to about 6 hours.Preferably, the reaction is carried out within a time period of about 10minutes to about 2 hours. The polymerization temperature is not criticaland will generally be in a range of from about 15° to about 150° C.,preferably in a range of about 40° to about 90° C. If the polymerizationis carried out at a temperature above the boiling point of the reactionmixture, then reflux and/or elevated pressure can be used to maintainliquid conditions in the reaction medium.

Various materials are known to be detrimental to the lithiummetal-initiated polymerization. Particularly, the presence of carbondioxide, oxygen, water and alcohols should be avoided during theorganollithium-initiated polymerization reaction to produce the alkalimetal terminated macromer precursor.

It is also within the scope of this invention to use an unsaturatedinitiator such as vinyl lithium or allyl lithium. After thepolymerization the lithium end can simply be terminated in aconventional manner, i.e. with an alcohol, and the vinyl at the otherend provides the polymerizable entity; or the lithium can be reactedwith an olefinic halosilane to give an α,ω-olefin if some crosslinkingwere desired.

Subsequent to the above-described initiation of the macromer precursor,the resulting living aromatic polymer chain is capped to give a terminalα-olefin. This is done with an alkenyl halosilane having only onehalogen atom as represented by the following general formula

wherein n is an integer of from 0 to 16, preferably 0 to 6, R is analkyl generally having 1 to 10 carbon atoms and preferably methyl and Xis a halogen, preferably chlorine. Thereafter, the resultingα-olefin-terminated aromatic macromonomeric comonomer (macromer) isreacted with the α-olefin monomer (or monomers) described previously.

One embodiment of this invention is exemplified as follows

In this preferred embodiment, the alkyl alkali metal initiator isreacted with the monoalkenyl aromatic compound to give the livingaromatic polymer chain in the olefin solvent. This is the comonomerprecursor. Thereafter, this living aromatic polymer chain is reactedwith the alkenyl halosilane to give the macromer comonomer, also in thepresence of olefin solvent. Finally, the comonomer is copolymerized withα-olefin monomer in a solventless system (the only diluent beingα-olefin monomer). Most preferably, the diluent all through thisoperation is the same α-olefin as that used as the monomer in the finalcopolymerization reaction. However, any α-olefin monomer capable ofbeing liquid under the pressure and temperature conditions beingemployed can be used as the diluent. Preferred are C₄-C₁₂α-olefins, mostpreferably hexene, octene and decene.

Broadly then, the comonomer is represented by the general formula

where R′ is the remnant of the organollithium initiator, R″ is apolymerized arene unit, R is alkyl as noted above, x is an integersufficient that the comonomer exhibits a molecular weight within therange of 500-30,000, preferably 1000-21,000, most preferably 5000-20,000and n is an integer of from 0 to 16, preferably 0 to 6. Thus, oncopolymerization the side chains are represented by the general formula

The comonomer is employed in an amount sufficient to give incorporationof about 5 to 49 weight percent comonomer based on the total weight ofincorporated monomer and comonomer. Preferably, the incorporated weightof comonomer is within the range of 10 to 40, more preferably 15 to 35weight percent based on the total weight of the copolymer. The weightpercent glassy regions of the final polymer will closely approximate theweight percent comonomer since the backbone is essentially amorphous andthe polymerized comonomer chains pre-dominantly form glassy domains.

While the individual aromatic side chains are generally lower molecularweight than the end blocks of prior art thermoplastic elastomers, theystill form glassy domains to “crosslink” the polymer to give strengthwhile the amorphous backbone imparts elastomeric characteristics.

Thus, in this aspect of the first embodiment the thermoplastic elastomerto be functionalized is already complete whereas in the first twoaspects of the first embodiment, the side chains remain to be provided.

Methods for carrying out the copolymerization of the α-olefin backbonemonomer and the comonomer for all three aspects of the first embodimentof this invention include the use of metallocene or Ziegler-Nattacatalysis as well as cationic polymerization. Other methods include freeradical or Lewis acid catalyzed processes.

Metallocene catalysts are organometallic coordination compounds obtainedas a cyclopentadienyl derivative of a transition metal or metal halide.Their use in the polymerization of olefins is well known.

A useful Ziegler-Natta catalysis process is described in Asanuma, U.S.Pat. No. 5,045,597 (Sep. 3, 1991) which is herein incorporated byreference. The Ziegler-Natta method of polymerization requires thepresence of a catalyst which includes a transition metal compound andwhich also utilizes an aluminum compound as well as an electron donor.Such transition metal compounds include titanium halides such astitanium tetrachloride, magnesium alkoxide supported titaniumtetrachloride and certain metallocenes of zirconium, titanium, andhafnium which are known from the art to polymerize α-olefins. Thealuminum compound is usually an organo aluminum compound which ispreferably selected from the group consisting of trialkyl aluminum,dialkylaluminum halides, alkyl aluminum sesquihalides, alkyl aluminumdihalides and aluminoxanes. There are a wide variety of electron donorswhich can be used and they are usually oxygen or nitrogen containingcompounds such as ethers, esters, ortho ethers, alkoxy-siliconcompounds, and heterocyclic aromatic nitrogen compounds.

The Ziegler-Natta polymerization may be conducted in neat monomer, bysolvent polymerization, or by vapor phase polymerization. Generally, thepolymerization is conducted at a temperature of from 30° C. to 100° C.under a pressure of from atmospheric to the vapor pressure of the1-alkenyl functionalized monomer at the polymerization temperature andoptionally in the presence of a molecular weight control agent such ashydrogen.

Thermoplastic elastomers require an amorphous polymer backbone andglassy or semicrystalline polymer grafts. Other catalysts suitable forproducing amorphous polymer backbones are described in Job, U.S. Pat.No. 5,122,494 (Jun. 16, 1992), Job, U.S. Pat. No. 5,089,573 (Feb. 18,1992), Job et al, U.S. Pat. No. 5,118,768 (Jun. 2, 1992), Job, U.S. Pat.No. 4,874,737 (Oct. 17, 1989), Wilson et al, U.S. Pat. No. 4,971,936(Nov. 20, 1990), and Job et al, U.S. Pat. No. 5,229,477 (Jul. 20, 1993),which are all herein incorporated by reference.

A preferred catalyst for use herein is described in Job U.S. Pat. No.5,122,494 (Jun. 19, 1992). The catalyst is formed by contacting, in thepresence of an inert diluent, an alkyl aluminum halide halogenatingagent with a complex magnesium-containing, titanium-containing alkoxidecompound prepared by reaction of magnesium alkoxide, titaniumtetra-alkoxide and a phenolic compound. The complex alkoxide compoundsare of somewhat variable stoichiometry but have the general illustrativeformula

Mg₃Ti(OR′″)₈X₂

wherein R′″ independently is alkyl of up to four carbon atoms inclusiveand X independently is a monovalent anion derived from an electron donorsuch as a phenolic compound, aldehyde or ether as described herein. Thediluent is then removed to produce, as a particulate solid, the complexalkoxide compound. This solid is treated with alkyl aluminum halide toproduce the olefin polymerization catalyst.

The preferred alkoxides are magnesium ethoxide, Mg(OEt)₂, andtitanium-tetraethoxide. The phenolic compound is selected from phenol oran activated phenol (a monohydroxylic phenol of one aromatic ring havingaromatic ring substituents other than hydrogen which serve to alter thepKa of the phenolic compound). Suitable phenolic compounds are phenol,o-cresol, and 2,6-di-t-buty-4-methylphenol (BHT). An election donor asdescribed hereinabove or hereinbelow can also be used.

The α-olefin backbone monomer and the comonomer may be cationicallypolymerized by reacting them in the presence of a cationicpolymerization initiator in the presence of a Lewis acid and, generally,an electron donor. The Lewis acid and the electron donor may becomplexed together. Lewis acids which can be utilized herein includemetal halides, such as aluminum trichloride (and molten salts containingaluminum trichloride), boron trichloride, boron trifluoride and titaniumtetrachloride, and organometallic derivatives, such asethylaluminumdichloride and triethyl aluminum, and oxyhalides, such asphosphorus oxychloride. Electron donors which are useful herein includealkyl amines, pyridines, such as 2,6-lutidiene and 2,4,6-collidine,triaryl or trialkyl phosphines, benzaldehyde, ethers such as1,2-dioxybenzene and veratrole. The cationic polymerization initiatorsare generally taken from the group consisting of tertiary alkyl halidessuch as t-butylchloride and triphenymethylfluoride.

The preferred Lewis acids are aluminum trichloride and boron trichloridebecause of their higher activity. The preferred electron donors are2,6-lutidine and benzaldehyde because they have been shown to giverandom copolymers and highly amorphous polymers, respectively (Job etal, U.S. Pat. No. 5,134,209 (Jul. 28, 1992) and the Job U.S. Pat. No.5,229,477 patent. The preferred cationic polymerization initiators arecumyl-type derivatives like cumylchloride, alkoxide, or aliphatictertiary chlorides.

The cationic polymerization may be a batch, semi-continuous, or acontinuous process. Generally, the polymerization is carried out at atemperature of from about −100 to about 0° C. under a pressure of from 0to 10 atm. Another method for copolymerizing the α-olefins and thefunctionalized monomers is free radical polymeriazation.

In the second embodiment of the invention, the backbone is simply aconventional ethylene/propylene diene monomer (EPDM) polymer which ismetallated in a manner known in the art so as to provide sites for theanionic polymerization of a monovinylarene anionically polymerizablemonomer “from” the backbone. The production of the EPDM polymers and thelithiation thereof are known in the art as shown in Lund et al, U.S.Pat. No. 4,786,689 (Nov. 22, 1988); and Lund et al, U.S. Pat. No.4,794,145 (Dec. 27, 1988), the disclosures of which are herebyincorporated by reference. These reactions generally involve themetallation of allylic sites in the olefinic moieties of the dienemonomer by reaction with alkyllithium compounds in the presence ofactivators. These lithiated sites then serve as initiator sites toinitiate the polymerization of subsequently added anionicallypolymerizable monomer.

Side Chain Formation—First Embodiment

In the first aspect of the first embodiment of this invention, a livingaromatic polymer side chain is produced by anionic polymerization asdescribed hereinabove with regard to the preparation of the olefinterminated polystyrene comonomer in the third aspect of the firstembodiment of this invention. The only difference being that instead ofterminating the living polymer with a alkenyl halosilane to give amacromer, the living polymer chain is left intact and reacted with thefunctional group supplied by the comonomer. This results in grafting theliving aromatic polymer chain to the amorphous backbone at the site ofthe comonomer incorporation.

By living polymer chains it is meant that the polymerization initiatoris still a part of the polymer chain and is active and available forfurther polymerization if more monomer becomes available. In this case,the polymerization is ended when the monomer supply is exhausted. Forexample, when polystyrene is polymerized and an organo lithium compoundis used as the initiator, the living polymer chain can be represented as

PS⁻Li⁺

This is known as polystyryl lithium.

A particularly desireable feature of this embodiment of the presentinvention is the ability to produce a saturated graft block copolymerwithout the necessity for a hydrogenation step. By “saturation” is meantno or essentially no aliphatic unsaturation. Saturated graft blockcopolymers are produced in the first aspect of this embodiment since theanionically polymerized monomer is one which contains a single aliphaticdouble bond. Examples are vinyl aromatic hydrocarbons, particularlystyrene, substituted styrenes, and ethylene. When these monomers areutilized the result is a saturated graft block copolymer.

The final step of the first aspect of this embodiment is accomplished asnoted above by grafting the living polymer chains onto the copolymer.For halosilane comonomers, this takes place by replacement of a halogenattached to the silicon with the living polymer chain. This isaccomplished by reacting the two polymers in the presence of anactivator such as tetramethylethylenediamine or ethers such as glyme(1,2-dimethoxyethane), o-dimethoxybenzene, or ethylene glycoldiethylether, at a temperature of 30 to 100° C. and a pressure of 1 to10 atm. This step also can be carried out in the absence of activatorsbut it proceeds more slowly to completion.

The copolymerization of the α-olefin and the 1-alkenyl functionalizedcomonomer produces a polymer with a saturated olefinic backbone havingpendent saturated alkyl chains having a functional group attachedthereto which may be a terminal group or which may be in the internalportion of the chain. Such copolymers may be represented by thefollowing:

The living polymer chains react with these copolymers at the silicontrichloride sites and the polymer chain takes the place of a chloride onthe silicon trichloride group in the polymer so that it becomes part ofa pendent side chain. In the case of a polystyryl lithium livingpolymer, the above copolymer is converted to a saturated graft blockcopolymer with the following formula:

In the second aspect of the first embodiment of the invention, thebackbone is metallated (“lithiated” when lithium is the metal) byreaction with a metal alkyl or aryl compound, especially alkyl lithium(RLi) compounds such as sec-butyl lithium or n-butyllithium in thepresence of a polar metallation activator. The RLi compound lithiates(metallates) one of the carbons, generally by abstraction of thebenzylic hydrogen. Thus, in the context of this invention the benzylicposition constitutes a functional group as noted previously. Thisresults in the following structure when n is 0:

When n is 1 to 20 it results in the following structure:

Some metallation of the benzene ring itself can also occur. In anyevent, the resulting

then serves as a subsequent initiation site for anionicallypolymerizable monomers to polymerize out “from” the backbone to producependant side chains.

An activator is generally required to catalyze the metallation reaction.Suitable activators include tertiary aliphatic amines, tertiarydiamines, and triamines. Preferred activators include dipiperidinoethaneand tetramethyl-ethylene-diamine (TMEDA). The metallation reaction isgenerally carried out at 0 to 100° C., preferably 25 to 60° C. for atime within the range of 1 minute to 24 hours, preferably 30 minutes to1 hour. Suitable solvents for the metallation include saturatednon-aromatic solvents such as cyclohexane. Generally, the comonomer isemployed in an amount just sufficient to give about the number of sitesdesired for pendant chains. Accordingly, the metallation promoter isgenerally present in an amount of about 1 equivalent per polymerizedcomonomer unit. However, this could be subject to wide variation. Forinstance, more sites could be incorporated into the backbone thannecessary and hence less than a stoichiometric amount of metallationagent would be used. Alternatively, an excess may be used so as to speedup the metallation with excess thereafter being removed. More detailconcerning the metallation can be found in Gergen and Lutz, U.S. Pat.No. 4,898,914 (Feb. 6, 1990), the disclosure of which is herebyincorporated by reference. All of the conditions broadly set out in theabove-described patent are applicable herein.

Once the metallation reaction is complete, there will be a number ofmetallated sites on the copolymer which are available for growth ofanionically polymerized polymer side chains.

The final step of the process of preparing the polymer to befunctionalized in this second aspect of the first embodiment of thisinvention is accomplished, for example, by growing the living polymerchains from the lithiated α-olefin/vinyl aromatic copolymer byinitiation and subsequent polymerization from the lithiated sites withthe anionically polymerizable monomer. This is accomplished by reactingthe backbone metallated copolymer and the anionically polymerizablemonomer in a suitable solvent. Generally, reaction temperature rangesfrom about −150° C. to about 300° C., preferably 0° C. to 100° C.Reaction time generally ranges from about 5 minutes to about 24 hours,preferably 30 minutes to 3 hours. Reaction pressure is generally 1-10atmospheres.

As noted hereinabove, the polymer to be functionalized is alreadycomplete in the third embodiment of the first aspect of this inventionsince the comonomer itself is a macromer which carries the pendantaromatic site chain.

Side Chain Formation—Second Embodiment

In the second embodiment of this invention, the EPDM backbone polymer ismetallated as is known in the art and then a monoalkenyl aromaticmonomer grafted “from” the metallated site as in the second aspect ofthe first embodiment of the invention. This embodiment of the inventionis less preferred because from about 1 to 4% unsaturation remains in therubber backbone due to diene comonomer and these sites are prone todegradation in the presence of heat and/or chemicals resulting in theloss of material properties.

Functionalization

The amorphous backbone polymers of this invention can be functionalizedin the same manner as conventionally prepared thermoplastic elastomers.Such techniques are disclosed, for instance, in Gergen et al, U.S. Pat.No. 4,578,429 (Mar. 25, 1986), the disclosure of which is herebyincorporated by reference. Briefly, this can be described as follows.

In order to incorporate functionalities into the base polymer, monomerscapable of reacting with the base polymer, for example, in solution orin the melt, by free radical mechanism are necessary. Monomers may bepolymerizable or nonpolymerizable, however, preferred monomers arenon-polymerizable or slovenly polymerizing.

The monomers must be ethylenically unsaturated in order to take part infree radical reactions. It has been found that by grafting unsaturatedmonomers which have a slow polymerization rate, the resulting graftcopolymers contain little or no homopolymer of the unsaturated monomerand contain only short grafted monomer chains which do not separate intoseparate domains.

The class of preferred functionalizing monomers which will form polymerswithin the scope of the present invention have one or morefunctionalities or their derivatives such as carboxylic acid groups andtheir salts, anhydrides, esters, imide groups, amide groups, acidchlorides and the like in addition to at least one point ofunsaturation.

These functionalities can be subsequently reacted with other modifyingmaterials to produce new functional groups. For example a graft of anacid-containing monomer could be suitably modified by esterifying theresulting acid groups in the graft with appropriate reaction withhydroxy-containing compounds of varying carbon atom lengths. Thereaction can take place simultaneously with the grafting or in asubsequent post modification reaction.

The functionalized polymer will usually contain from 0.02 to 20,preferably 0.1 to 10, and most preferably 0.2 to 5 weight percent offunctionality.

The preferred functionalizing monomers are unsaturated mono- andpolycarboxylic-containing acids (C₃-C₁₀) with preferably at least oneolefinic unsaturation, and anhydrides, salts, esters, ethers, amides,nitriles, thiols, thioacids, glycidyl, cyano, hydroxy, glycol, and othersubstituted derivatives from said acids.

Examples of such acids, anhydrides and derivatives thereof includemaleic acid, fumaric acid, itaconic acid, citraconic acid, acrylic acid,glycidyl acrylate, cyanoacrylates, hydroxy C₁-C₂₀ alkyl methacrylates,acrylic polyethers, acrylic anhydride, methacrylic acid, crotonic acid,isocrotonic acid, mesacronic acid, angelic acid, maleic anhydride,itaconic anhydride, citraconic anhydride, acrylonitrile,methacrylonitrile, sodium acrylate, calcium acrylate, and magnesiumacrylate.

Other functionalizing monomers which can be used either by themselves orin combination with one or more of the carboxylic acids or derivativesthereof include C₂-C₅₀ vinyl monomers such as acrylamide, acrylonitrileand monovinyl aromatic compounds, i.e. styrene, chlorostyrenes,bromostyrenes, α-methylstyrene, and vinyl pyridines.

Other functionalizing monomers which can be used are C₄ to C₅₀ vinylesters, vinyl ethers and allyl esters, such as vinyl butyrate, vinyllaurate, vinyl stearate, and vinyl adipate, and monomers having two ormore vinyl groups, such as divinyl benzene, ethylene dimethacrylate,triallyl phosphite, dialkylcyanurate and triallyl cyanurate.

The preferred functionalizing monomers to be reacted with the blockcopolymers according to the present invention are maleic anhydride,maleic acid, fumaric acid and their derivatives. It is well known in theart that these monomers do not polymerize easily.

Of course, mixtures of functionalizing monomers can be also added so asto achieve functionalized copolymers in which the copolymer contains atleast two different functionalizing monomers therein.

Reaction temperatures and pressures should be sufficient to melt thereactants and also sufficient to thermally decompose the free radicalinitiator to form the free radical. Reaction temperatures would dependon the base polymer being used and the free radical initiator beingused. Typical reaction conditions can be obtained by using a screw typeextruder to mix and melt the reactants and to heat the reactant mixtureto the desired reaction temperature.

The temperatures useful in the reaction of the process of the presentinvention may vary between wide limits such as from +75° C. to 450° C.,preferably from about 200° C. to about 300° C.

It is to be noted that since the side chain-containing backbone isalready formed before this functionalization, the functional groups areattached directly to the block copolymer as opposed to already being onthe chain and serving as a site for the side chains.

Definitions

As used herein “functionalized,” “functionalizing” and “functionality”refer to the final treatment with the component containing at least onepoint of saturation such as maleic anhydride. “Functional group” and“functional to” refer to characteristics of the comonomer used in thesecond aspect of the first embodiment of this invention.

Utility

The block copolymers, as modified, can still be used for any purpose forwhich an unmodified material (base polymer) was formerly used. That is,they can be used for adhesives and sealants, or compounded and extrudedand molded in any convenient manner.

EXAMPLE

Melt Phase Functionalization of Poly(α-olefin)-g-Polystyrene Polymerswith Maleic Anhydride

Maleic anhydride functionalization of two α-olefin backbonethermoplastic elastomers and one EPDM backbone thermoplastic elastomerwas studied. A conventional thermoplastic elastomer prepared forcomparison with the invention by sequentially polymerizing styrene,butadiene and then styrene followed by termination of the polymerchains, hydrogenation and hydrogenation catalyst removal was used as acomparison polymer. This polymer was used since such polymers are knownto efficiently graft maleic anhydride in the melt in the presence of anorganic peroxide. Characteristics of the polymers used are given inTable 1. Maleic Anhydride powder was dry blended with the polymer crumb,and 0.2 wt % 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (sold under thetradename Lupersol 101 by Lucidol Pennwalt) was dispersed into themixture as a 0.5 wt % solution in acetone. The mixtures were blended ina Custom Scientific Instruments melt mixer with a 5 cm³ capacity at200-210° C. and 70-80 rpm for one minute. The products were thenanalyzed by FTIR to determine the weight % maleic anhydride grafted tothe polymers. In addition, films were cast from toluene andstress/strain properties measured for comparison with the polymersbefore functionalizing.

Results of free radical functionalizing grafting are given in Table 2.

Sample KT-24H was prepared in accordance with the first embodiment,first aspect of this invention. Specifically, 1-hexene and 2 mole %allyl dimethyl-chlorosilane were copolymerized using aMg₆(OCH₂CH₃)₁₀TiCl₄(benzaldehyde)₂ catalyst with an ethyl aluminumdichloride cocatalyst to give an amorphous copolymer. Styrene waspolymerized using a sec butyl lithium initiator and the resulting livingpolystyrene chains reacted with the copolymer to give saturatedthermoplastic elastomer.

AZN-4A was prepared in accordance with the first embodiment, secondaspect. Specifically, octene and 4-phenyl-1-butene were copolymerizedusing a Mg₆(OXCH₂CH₃)₁₀TiCl₄(benzaldehyde)₂ catalyst with atriethylaluminum co-catalyst to give an amorphous polymer. The resultingpolymer was metallated with secondary butyllithium usingN,N,N′,N′-tetramethyl ethylenediamine as a promoter. Separately, styrenewas introduced and a styrene polymer chain formed by anionicpolymerization from the metallation site which acted in the manner of aconventional initiator.

ZNA-2G contains a backbone of a commercial EDPM sold under the tradenameNordell 1320 by DuPont. This material was then maleated and styrenegrown from the metallation site as in AZN-4A above.

The composition labeled “comparison” was prepared as describedhereinabove.

TABLE 1 Polymer Characteristics Number of Polystyrene PolystyreneGrafts/ Content MW 100K backbone Polymer Structure (%)^(c) (g/mole)^(f)Mw^(i) KT-24H C₆-g-PS^(a) 31 6000^(g) 7.5 AZN-4A C₈-g-PS^(b) 22 6000^(g)4.7 ZNA-2G EPDM-g-PS^(c) 43 9000^(g) 8.4 Comparison S-EB-S^(d) 307200/7700^(h) — ^(a)Poly(1-hexene)-g-polystyrene^(b)Poly(1-octene)-g-polystyrene ^(c)EPDM-g-polystyrene^(d)Styrene-Hydrogenated Butadiene-Styrene triblock copolymer^(e)Determined by ¹H NMR ^(f)Determined by GPC ^(g)Values reported arefor each polystyrene graft ^(h)Values reported are for first and secondpolystyrene block${\quad^{i}{Calculated}\quad {using}\quad {the}\quad {following}\quad {equation}\text{:}\quad {Ng}} = \frac{100\text{,}000 \times {wg}}{{Mg} \times ( {1 - {wg}} )}$

where Ng = number of grafts per 100,000 g/mole of backbone wg = weightfraction of graft (PS) in the graft copolymer Mg = number averagemolecular weight of the graft (PS) in the graft copolymer

TABLE 2 Tensile Properties^(c) Tensile Properties^(c) Before MaleicAfter Maleic Anhydride Grafting Anhydride Grafting MA MA Graft UltimateUltimate Ultimate Ultimate Added grafted^(a) Efficiency^(b) StrengthElongation Strength Elongation Sample (wt %) (wt %) (%) (psi) (%) (psi)(%) KT-24H 2.3 0.3 9.6 342 ± 35  239 ± 101 205 ± 46  126 ± 55 AZN-4A 2.30.32 14 830 ± 58  1166 ± 77  323 ± 4  204 ± 4  ZNA-2G 2.3 0.57 25 2574 ±582  909 ± 66  1379 ± 106  428 ± 18 Comparison 3.1 0.97 42 6439 ± 231 681 ± 20  3097 ± 403  725 ± 29 ^(a)Deternined by FTIR using anexperimentally determined correlation between polystrene absorbance andcarbonyl absorbance ^(b)Calculated as follows:${\% \quad {Graft}\quad {efficiency}} = {( \frac{\% \quad w\quad {MA}\quad {Grafted}}{\% \quad w\quad {MA}\quad {Added}} ) \times 100}$

^(c)Test performed on an INSTRON ® Model 4505 with a gauge length of 1inch and a cross head speed of 1 inch/min. Values reported are the mean± s.d. of at least three independent measurements on compression moldedfilms.

As can be seen, the expected Beta-scission did not reduce the materialto a useless condition. Perhaps less Beta-scission occurred than wouldhave been predicted or perhaps this surprising result reflects the factthat there are more polystyrene blocks per polymer chain than in aconventional triblock copolymer and thus a significant fraction of thepolymer backbones still contain at least two grafts to form a mechanicalnetwork. Furthermore, when conventional thermoplastic elastomers arehydrogenated and functionalized, some aliphatic unsaturation generallyremains and some of the aromatic unsaturation is destroyed. Here, thesaturated elastomers have no or essentially no aliphatic unsaturationand all of the original aromatic unsaturation remains.

While this invention has been described in detail for the purpose ofillustration, it is not to be construed as limited thereby but isintended to cover all changes and modifications within the spirit andscope thereof.

What is claimed is:
 1. A process for producing a functionalizedsaturated thermoplastic elastomer comprising: (a) copolymerizing, underpolymerization conditions to form a thermoplastic elastomer (i) amonomer system selected from (a) at least one C₄ to C₃₀ α-olefin and (b)ethylene with 20 to 40 mole percent of a higher α-olefin, and (ii) acomonomer of the general formula

wherein R′ is the remnant of an initiator, R″ is a polymerizedmonoalkenyl arene unit, R is alkyl, n is an integer of from 0 to 16, andx is an integer sufficient to give said monomer a molecular weightwithin the range of 500-30,000; and (b) contacting said thermoplasticelastomer with a free radical initiator and a functionalizing monomerhaving at least one point of unsaturation.
 2. A method according toclaim 1 wherein said functionalizing monomer is selected from carboxylicacids and derivatives of carboxylic acids.
 3. A method according toclaim 1 wherein R′ is the remnant of an unsaturated initiator, saidcomonomer thus being an α,ω-olefin.
 4. A method according to claim 1wherein (a) said comonomer is formed by reacting an alkyl alkali metalinitiator with a monoalkenyl aromatic compound to give a living aromaticpolymer chain said reacting being done in an α-olefin solvent selectedfrom C₆ to C₃₀ olefins; (b) thereafter reacting said living aromaticpolymer chain with an alkenyl halosilane in the presence of a solventwhich is an α-olefin selected from C₄ to C₃₀ α-olefin; and (c)thereafter reacting said comonomer with a monomer which is an α-olefinselected from C₄ to C₃₀ α-olefins to give a saturated thermoplasticelastomer, no other solvent being used in said method.
 5. A methodaccording to claim 4 wherein said α-olefin of (a), (b), and (c) is thesame α-olefin.
 6. A method according to claim 1 wherein said monomersystem is a single monomer selected from octene and decene, saidcomonomer is the reaction product of a living polystyrene lithium chainand 6-hex-1-enyl dimethylchlorsilane, said copolymerizing is done in thepresence of a transition metal catalyst.
 7. A composition produced bythe method of claim
 6. 8. A composition produced by the method ofclaim
 1. 9. A process for producing a functionalized saturatedthermoplastic elastomer which comprises: (a) copolymerizing: (i) amonomer system selected from at least one C₄ to C₃₀ α-olefin andethylene plus 20 to 40 mole percent of a higher α-olefin with (ii) acomonomer formed by terminating a living polystyrene-lithium chainhaving a vinyl group at an end of said chain opposite the thusterminated lithium to produce a thermoplastic elastomer; and (b)contacting said thermoplastic elastomer with a functionalizing monomerhaving at least one point of unsaturation.